This invention relates to a luminosity detector for an internal combustion engine, a method for operating an internal combustion engine and an improved method for measuring the temperature of a component of an internal combustion engine.
Efforts have been made to analyze the combustion process occurring within the combustion chamber of an internal combustion engine through the use of luminosity detectors. Such detectors normally employ some form of window or probe that will transmit light from the combustion chamber to a photodiode that outputs an electrical signal that is related to the luminosity within the combustion chamber. Although this type of device has been utilized for certain experimental purposes and also for detecting such abnormal running conditions as knock in an engine, it has been found that this signal can be utilized to measure and control a number of engine operating parameters. Applications of this principle are disclosed in the copending applications entitled "Method of Operating an Engine", Ser. No. 193,918, filed May 13, 1988 and its continuation in part application entitled "Method of Operating An Engine And Measuring Certain Operating Parameters", Ser. No. 266,682, filed Nov. 3, 1988, each filed in the name of Steven L. Plee, et al. These disclosures are incorporated herein by reference.
As noted in the aforenoted copending applications, the use of a luminosity detector can present a very significant tool in not only engine measurement but also engine control. The various types of controls possible and measurements which may be made are disclosed in those applications and need not be repeated here.
In applications of luminosity detectors to detect the conditions in a combustion chamber, there are a number of problems which may arise. Specifically, the luminosity detector employs a photodiode which is normally mounted in or adjacent to the cylinder head. As is well known, the responsivity (sensitivity to light) and dark current, sometimes called reverse saturation current, (output of the device in a no-light condition) change with temperature.
As is well known, the components of an engine undergo considerable temperature variations during the engine operation. Since the combustion chamber is normally formed in the cylinder head and the luminosity detector is mounted there, it is positioned in a place where the maximum or near maximum temperature variations may exist. For example, under extreme cold start conditions the sensor may be exposed to a temperature as low as -30.degree. F. On the other hand, after hot soak, the sensor may get as hot as 300.degree. F. Of course, these temperature variations and their effect on the responsivity and dark current, as aforenoted, can present problems in connection with the use of these devices to either measure or control an engine.
It is therefore, a principal object of this invention to provide an improved arrangement for measuring the luminosity in an internal combustion engine by means of a luminosity detector.
It is a further object of this invention to provide an improved method for controlling an engine using a luminosity detector wherein temperature compensation is not required.
It is a further object of this invention to provide a self temperature compensated luminosity detector for an internal combustion engine for measurement and control purposes.
As has been previously noted, the dark current of a photodiode varies with the engine temperature. It is, therefore, another object of this invention to provide an improved arrangement for compensating for the changes in luminosity detector sensitivity by providing temperature compensation.
It is a further object of this invention to provide an improved method for measuring engine operating parameters and controlling the engine using a luminosity detector that will compensate for temperature variations.
In view of the fact that the dark current of a photodiode varies with temperature, it has been discovered that the photodiode can be utilized for other purposes in addition to luminosity measurement. For example, by placing the photodiode in heat exchanging relationship with a component of the engine, the temperature of the engine component can be measured by sensing the dark current of the photodiode.
It is, therefore, a still futher object of this invention to provide an improved and simplified arrangement for measuring the temperature of an engine component.